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Using RFID Tags Around the House?
Attacked-by-gremlins writes "I have a larger family and various items in the house (some tools, some pieces of clothing) 'travel' unexpectedly. We joke about gremlins doing that, but it's tiring never to be sure that I'll find an object where I left it two days ago. For the sheer hacking fun of it, I'm thinking of sticking RFID tags on some and trying to triangulate a position with several tranceivers placed in the house. Has anyone have any suggestions for this amateur 'Google Home'? Thanks."
There's some equipment out there with decent range, but it's usually quite expensive. My $50 do-it-all tranciever has a range of about 6 inches. With the lower frequency tags you get better range, but still I don't think I've seen trancievers with anywhere-in-the-house type range.
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Really. Most sub $100 readers have a range that can be measured in millimeters. To get something with about 3' or 4' of range for a single reader will cost four figures. I've done some fairly extensive testing with these readers, and it is possible to boost the range by adding external antennas (for more money). So I guess what I am saying is that what you are planning on doing is technically possible, but is not feasible for most peoples' "tinkering" budgets.
I don't know what your budget is like, but the readers can be pricey. The ones we use that are able to triangulate (2-D with two readers, 3-D with 3 readers) ran about $4k apiece. But, they would easily cover a standard sized home.
Of course, we had different needs than you, so there are probably considerably cheaper alternatives.
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It seems most people here don't seem to understand active rfid vs. passive rfid.
Passive:
pro - Tags are extremely small, readers are cheap, tags are cheap
con - Range, non-existant
Active:
pro - Range
con - expensive tags, tags are large, tags are battery powered
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As others have mentioned the range for passive RFID detection is painfully short - to do what OP wants he needs active tags and readers.
A passive RFID tag is powered by the reader - hence its short range. An active tag carries its own power supply - like the toll booth speedpass tags.
Active tags run from about the size of a dime to about the size of a paperback book - in my job I deal with the paperback book-sized tags.
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Looks like the idea has already been patented.
http://www.patentstorm.us/patents/7295132/description.html
Probably not RFID. I haven't seen much of anything that offers a signal strength measurement with enough granularity. In addition, signal strength is dependent on what direction the antenna(on the tag) is facing.
I don't know of anything out there commercially available with a precise enough clock to manage it time based.
You can get up to about 10 feet with certain UHF tags and receivers, but that is really pushing FCC limitation on signal power. RFID tags really just aren't locators, regardless of how much we want them to be.
I use a product called Homeseer and alot of people are already doing this. There are two types of tags people are using, iAutomate tags and cheaperRFID tags. The iAutomate tags are more complex, and hence more expensive. I have the Cheaper RFID tags. I have one in our laptops bags-- if no laptops are present-- no wifi. I don't believe they do triangulation. The iAutomate ones do- but are far more expensive-- at least when I last looked.
Assuming you really mean disciplpine, and not just using the word as a euphemism for punishment, I agree with you. But, do some child development research: by the age of 2 the little terrorists barely know right from wrong in general, and are just coming to grasp with the awareness of the difference between self and others. By the age of 4 they should know which stuff of Dad's and Mom's they should not touch (though they'll still touch it occasionally)
You clearly do not have children. It's easy to find everything when you're the only one using it, and you make sure to put it back where it belongs after every use. Add a few more people into the mix, not so easy.
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Promoting critical thinking since 1994.
Keep an eye on e-bay. Suggest you get some of the early RFID readers that are out there. Matrics/Symbol/Motorola AR400 is a start.
.02 seconds. The hardiest of tags will survive mild washing, freezing etc.
You'll need antennas, 900Mhz 6dBi gain are the most popular.
Using the AR reader you can put it into autonomous mode (it will read tags all by itself). A quick web based application cat hit the readers on occassion to see which antenna picked up a particular tag last.
Now, tag everything - old tax returns, TV remote etc. Perhaps car keys.
Be aware that RF has limitations. Dropping your keys in a fish tank will normally obscure the RFID - however, you should be able to tell which room it is in (where it was seen last).
Next, add tags to all the people (and dogs) in the house. Now, when the keys were last scene in the living room, you can correlate that with who was in the living room at that time - and even later.
The RFID readers are limited to 1Watt (30dBm) in the US by FCC, so you really want to pay attention to cables. I'm not sure what antennas go for, but you can make reasonable antannas yourself. On a reader like the AR400, you want to make a RHCP for transmit and a LHCP for receive (gives nice isolation) or vice versa.
Love to here how it turns out.
BTW, microwave ovens will kill tags in about
Some tags, if unprotected, will temporarily fail under intense incondensable lights. Turn off light and they will work again. Special tags will work well on metal (spaced off the metal by 1/8" or so). Yet other special tags will under water... Some of the biggest tags can be read at 40+ feet. The small ones, say 1"x1" are only good for a few inches. Size matters.
Class 0 has some performance advantages, but no one is making them anymore - maybe you can get some used ones cheap. The AR400 reader can read them as well.
BTW, if you have 900Mhz wireless phones (or other devices) in the house, forget it.
Look for "gen 2" (Specifically EPC Class 1 Generation 2) equipment.
That is exactly what you are looking for.